The present invention relates to a paper conveying apparatus of a sheet-fed press, which grips, with conveying grippers, the end portion of a sheet conveyed from upstream in the paper conveying direction and supplies the sheet to a printing cylinder.
Generally, in a paper conveying apparatus of this type, sheets are drawn and conveyed by suction one by one by the suction port of a sucker unit from a paper feed unit. Each sheet is then fed onto a feeder board by rotation of a paper feed roller, and conveyed on the feeder board toward a feed board by a paper feed tape or the like. When the sheet is fed onto the feed board, its leading end is aligned by a registration portion, and the sheet is gripped by, e.g., the grippers of a swingable swing unit. Then, the sheet is conveyed to the cylinder of the printing press by the pivotal movement of the swing unit, and re-gripped by the grippers of the cylinder.
In the paper conveying apparatus of this type, the trailing side of the paper expands or shrinks in the right-to-left direction due to water and a large pressure which are applied when the sheet is subjected to printing. When this expansion or shrinkage occurs, misregistration occurs in printing registration called fan-out registration at the trailing side of the paper during multi-color printing, to cause defective printing.